In continuous ink jet printing of the multiple jet type, ink is circulated under pressure to project from a plurality of orifices formed in a linear array along an orifice plate. The projected ink jets are stimulated to break off adjacent charge electrodes; and, in the usual, binary printing approach, charged drops are field-deflected to a catcher, with non-charged drops continuing to the print medium.
Commercial systems employing the continuous binary ink jet approach have been successfully employed using longer (e.g. page width) orifice plates of lower resolution (e.g. 120 orifices per inch) and shorter (e.g. line height) orifice plates having high resolution (e.g. 300 orifices/inch). Intermediate length orifice arrays having intermediate resolution have also been used successfully.
The short orifice plates have been used in moving print heads which traverse lines of the print media successfully moved therepast. The long and intermediate length orifice plates have been used with stationary print heads, but suffer the problems of lower resolution. To provide the ability to address wider swaths of the print media, with stationary print heads at higher resolution, with stationary print heads it has been suggested to stagger long, low resolution orifice plates in interleaved positions along the print media path. This requires great precision in alignment and in media-movement/drop address synchronization to yield acceptable quality, and has not commercially been feasible.
Thus, there has been a continuing need for ways to provide relatively longer, high resolution orifice plates, to enable reliable stationary-printhead address of large widths of moving print. A large number of techniques have been utilized for orifice plate fabrication; however, the most successful for forming high resolution orifice plates with precisely uniform size orifices has been the electroform method described in U.S. Pat. No. 4,184,925. In this approach, precisely sized photoresist pegs are formed on an electroplating substrate and the orifice plate is electroplated up to the top of the pegs and slightly thereover to achieve a precise diameter that is regulated by the plating time period. This fabrication method has been achieved successfully with shorter length orifice plates; however, precise orifice size uniformity has not heretofore been achieved with longer length arrays.